Add functions to rotate by quarter turns (#669)

src/geometric_transformations.rs

@@ -317,6 +317,146 @@ where
     warp(image, &projection, interpolation, default)
 }
 
+/// Rotates an image 90 degrees clockwise.
+///
+/// # Examples
+/// ```
+/// use imageproc::geometric_transformations::rotate90;
+/// use imageproc::gray_image;
+///
+/// let image = gray_image!(
+///     1, 2, 0, 0;
+///     3, 4, 0, 0;
+///     0, 0, 0, 0;
+///     0, 0, 0, 0);
+///
+/// let rotated = rotate90(&image);
+///
+/// assert_eq!(rotated, gray_image!(
+///     0, 0, 3, 1;
+///     0, 0, 4, 2;
+///     0, 0, 0, 0;
+///     0, 0, 0, 0));
+/// ```
+pub fn rotate90<P>(image: &Image<P>) -> Image<P>
+where
+    P: Pixel,
+{
+    let (width, height) = image.dimensions();
+
+    let mut rotated = Image::new(height, width);
+
+    for y in 0..height {
+        for x in 0..width {
+            rotated.put_pixel(height - y - 1, x, *image.get_pixel(x, y));
+        }
+    }
+
+    rotated
+}
+
+/// Rotates an image 270 degrees clockwise.
+///
+/// # Examples
+/// ```
+/// use imageproc::geometric_transformations::rotate270;
+/// use imageproc::gray_image;
+///
+/// let image = gray_image!(
+///     1, 2, 0, 0;
+///     3, 4, 0, 0;
+///     0, 0, 0, 0;
+///     0, 0, 0, 0);
+///
+/// let rotated = rotate270(&image);
+///
+/// assert_eq!(rotated, gray_image!(
+///     0, 0, 0, 0;
+///     0, 0, 0, 0;
+///     2, 4, 0, 0;
+///     1, 3, 0, 0));
+/// ```
+pub fn rotate270<P>(image: &Image<P>) -> Image<P>
+where
+    P: Pixel,
+{
+    let (width, height) = image.dimensions();
+
+    let mut rotated = Image::new(height, width);
+
+    for y in 0..height {
+        for x in 0..width {
+            rotated.put_pixel(y, width - x - 1, *image.get_pixel(x, y));
+        }
+    }
+
+    rotated
+}
+
+/// Rotates an image 180 degrees clockwise.
+///
+/// # Examples
+/// ```
+/// use imageproc::geometric_transformations::rotate180;
+/// use imageproc::gray_image;
+///
+/// let image = gray_image!(
+///     1, 2, 0, 0;
+///     3, 4, 0, 0;
+///     0, 0, 0, 0;
+///     0, 0, 0, 0);
+///
+/// let rotated = rotate180(&image);
+///
+/// assert_eq!(rotated, gray_image!(
+///     0, 0, 0, 0;
+///     0, 0, 0, 0;
+///     0, 0, 4, 3;
+///     0, 0, 2, 1));
+/// ```
+pub fn rotate180<P>(image: &Image<P>) -> Image<P>
+where
+    P: Pixel,
+{
+    let mut out = image.clone();
+    rotate180_mut(&mut out);
+    out
+}
+#[doc=generate_mut_doc_comment!("rotate180")]
+pub fn rotate180_mut<P>(image: &mut Image<P>)
+where
+    P: Pixel,
+{
+    let (width, height) = image.dimensions();
+
+    for y in 0..height / 2 {
+        for x in 0..width {
+            let x180 = width - x - 1;
+            let y180 = height - y - 1;
+
+            let p = *image.get_pixel(x, y);
+            let p180 = *image.get_pixel(x180, y180);
+
+            image.put_pixel(x, y, p180);
+            image.put_pixel(x180, y180, p);
+        }
+    }
+
+    if height % 2 != 0 {
+        let y_middle = height / 2;
+
+        for x in 0..width / 2 {
+            let x180 = width - x - 1;
+
+            let p = *image.get_pixel(x, y_middle);
+            let p180 = *image.get_pixel(x180, y_middle);
+
+            image.put_pixel(x, y_middle, p180);
+            image.put_pixel(x180, y_middle, p);
+        }
+    }
+}
+
 /// Translates the input image by t. Note that image coordinates increase from
 /// top left to bottom right. Output pixels whose pre-image are not in the input
 /// image are set to the boundary pixel in the input image nearest to their pre-image.